The relic abundance of heavy stable particles charged under a confining gauge group can be depleted by a second stage of annihilations near the deconfinement temperature. This proceeds via the formation of quarkonia-like states, in which the heavy pair subsequently annihilates. The size of the quarkonium formation cross section was the subject of some debate. We estimate this cross section in a simple toy model. The dominant process can be viewed as a rearrangement of the heavy and light quarks, leading to a geometric cross section of hadronic size. In contrast, processes in which only the heavy constituents are involved lead to mass-suppressed cross sections. These results apply to any scenario with bound states of sizes much larger than their inverse mass, such as U(1) models with charged particles of different masses, and can be used to construct ultra-heavy dark-matter models with masses above the naïve unitarity bound. They are also relevant for the cosmology of any stable colored relic.
Bibliographical noteFunding Information:
We thank Yuval Grossman, Marek Karliner, Teppei Kitahara, Peter Lepage, Michael Pe-skin, Jon Rosner, Ben Svetitsky, John Terning and especially Markus Luty for useful discussions. OT thanks Barak Hirshberg for his insight in molecular quantum mechanics. The authors are grateful to the Mainz Institute for Theoretical Physics (MITP) and to the Aspen Center for Physics, supported in part by NSF-PHY-1607611, for hospitality and partial support during the completion of this work. This work is supported by the Israel Science Foundation (Grant No. 720/15), by the United-States-Israel Binational Science Foundation (BSF) (Grant No. 2014397), by the ICORE Program of the Israel Planning and Budgeting Committee (Grant No. 1937/12). MG is supported by the NSF grant PHY-1620074 and the Maryland Center for Fundamental Physics. SI is supported at the Technion by a
fellowship from the Lady Davis Foundation and at Padova University by the MIUR-PRIN project 2015P5SBHT 003 “Search for the Fundamental Laws and Constituents”. GL acknowledges support by the Samsung Science & Technology Foundation. OT is supported in part by the NSF grant PHY-1719877.
© 2018, The Author(s).
- Phenomenological Models
- QCD Phenomenology